By end-to-end anastomosis basically an (artificial) anastomosis is understood in which two hollow organ sections (e.g. intestine parts) are re-sutured at their opened ends so that a fluid-tight and continuous course is formed. It is important in this context that the circumferential suture results in a completely fluid-tight as well as flexible and tear-resistant connection of the two hollow organ sections to be connected which is configured so that an as smooth surface as possible is formed at the inside of the hollow organ to ensure an interference-free fluid flow inside the hollow organ.
In the state of the art staple devices in the form of single-use instruments are known, as disclosed in DE 43 27 233 A1 for example. Consequently, a staple device of this type includes an endoscope shaft at the proximal end portion of which a handpiece for holding the device as well as for actuating a staple mechanism is disposed. The staple mechanism consists of a staple magazine distally fixed at the endoscope shaft approximately in the form of a cylindrical cartridge sleeve in which a number of staples circumferentially arranged on a circle are supported in a spring-biased manner as well as of a staple head or staple cap which is placed in a mushroom-like manner at the axially distal end of the cartridge sleeve and is axially movably guided in the cartridge sleeve by means of a pin fixed thereto. The stapling head is thus adapted to be continuously distanced from the cartridge sleeve in the axial direction of the staple device, thereby an adjustable circumferential (annular) axial clearance resulting between the stapling head and the cartridge sleeve, into which clearance the two ends of the hollow organ to be connected can be clamped. The staple head (or staple cap) as well as the cartridge sleeve are operable via suitable transmission means inside the endoscope shaft from the handpiece.
The problem of staple devices of this type basically consists in providing a fluid-tight as well as flexible and tear-resistant suture. For this purpose, in some staple devices two staple rows distanced in the radial direction of the cartridge sleeve are provided whose staples overlap in their engaging areas. Although the degree of tightness and the tear resistance are improved in this way, radially inwardly protruding tissue lobes or folds are necessarily formed, whereby a fluid flow inside the hollow organ can be hindered. For this reason, staple devices of this type recently have been replaced or supplemented by medical instruments, preferably having a bipolar electrode structure.
In the present case, too, such instrument includes an endoscope shaft comprising a proximal handpiece and an endoscope head preferably mechanically as well as electrically connected to the handpiece via appropriate transmission means inside the endoscope shaft. The endoscope head substantially consists of a bearing sleeve which is fixedly attached to the distal end portion of the endoscope shaft in an axially connected manner and at the distal front end of which a first circumferential electrode (electrode ring) is mounted, and of a relatively movable electrode shield (electrode cap). For this purpose, the electrode shield includes an axial pin movably guided in the bearing sleeve and coupled/adapted to be coupled to a mechanical transmission means inside the endoscope shaft for operating the same via the handpiece as well as a circumferential electrode rim arranged at the distal end of the pin on the same. The electrode rim supports, at the end face thereof facing the bearing sleeve, a second circumferential electrode (electrode ring) interacting with the first electrode.
In conformity with the staple devices known per se also in the instrument of this design, by axially moving the electrode shield through the handle an axial clearance can be set between the electrode rim and the bearing sleeve so as to clamp tissue to be connected there between and to coagulate (weld or seal) the same by charging the electrodes with HF current. By this method a flexible and fluid-tight tissue suture is formed without large tissue folds protruding into the interior of the hollow organ.
However, in instruments of this type the problem exists that at least the shield has to pass the joint without lastingly injuring the same when the instrument is removed from the hollow organ. There is always the risk that the HF current supply is inadvertently activated, whereby tissue can possibly be damaged especially in the area of the joint.